This application is based upon and claims the benefit of priority from Korean Patent Application No. 2003-66499, filed on Sep. 25, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The invention relates to a disk drive, and more particularly, to an apparatus and method for controlling head loading in a disk drive, which can reduce the possibility of collision between a head and a rotating disk when the head is loaded onto the rotating disk.
2. Description of the Related Art
A hard disk drive (HDD) is a computer data storage device, which reproduces data stored on disks or records data on the disks using a read/write head. In the HDD, a head is moved to a desired position by an actuator while flying above a data recording surface of a disk at a predetermined height.
FIG. 1 is a schematic plan view of a related art HDD, and FIG. 2 is an enlarged view of a ramp and a suspension of an actuator in the HDD of FIG. 1.
Referring to FIGS. 1 and 2, the HDD includes a base member 10, a spindle motor 12 installed on the base member 10, a disk 20 fixedly mounted on the spindle motor 12, and an actuator 30. Actuator 30 moves a slider 34, on which a read/write head 35 for data reproduction and recording is mounted, to a predetermined position on the disk 20. The actuator 30 includes a pivot bearing 31 installed on the base member 10, a swing arm 32 rotatably coupled to the pivot bearing 31, a suspension 33, which is installed at one end of the swing arm 32 and elastically supports the slider 34 toward a surface of the disk 20, and a voice coil motor (VCM), which rotates the swing arm 32. The VCM includes a VCM coil 37 coupled to the other end of the swing arm 32, and a magnet 38 disposed above and below the VCM coil 37 to face the VCM coil 37.
The VCM rotates the swing arm 32 in a direction according to Fleming's left-hand rule due to interaction between current input to the VCM coil 37 and a magnetic field formed by the magnet 38. That is, when the HDD is turned on and the disk 20 begins to rotate in an arrow direction D, the VCM rotates the swing arm 32 counterclockwise (in an arrow direction A) to move the slider 34, on which the read/write head 35 is mounted, to a position on a data recording surface of the disk 20. The slider 34 flies above the surface of the disk 20 at a predetermined height due to a lift force generated by the rotating disk 20. At this time, the head 35 mounted on the slider 34 reproduces or records data from or on the data recording surface of the disk 20.
Meanwhile, when the HDD does not operate and the disk 20 does not rotate, the head 35 should be parked in a position other than the data recording surface of the disk 20 so as not to touch the data recording surface of the disk 20. For this, a ramp 40 is installed outside the disk 20, and the suspension 33 has an end-tab 36 protruding therefrom such that the end-tab 36 is seated on a support surface 41 of the ramp 40.
When the HDD is turned off and the disk 20 stops rotating, the VCM rotates the swing arm 32 clockwise (in an arrow direction B). Accordingly, the end-tab 36 is moved to be parked on the support surface 41 of the ramp 40. Through this, the head 35 is unloaded from the disk 20. On the contrary, when the HDD is turned on and the disk 20 begins to rotate, the end-tab 36 is moved from the support surface 41 of the ramp 40 and the head 35 is loaded on the disk 20 due to the counterclockwise rotation of the swing arm 32 as described above.
In the meantime, an actuator latch 50 locks the actuator 30 in any desired place so that while the read/write head 35 is parked on the ramp 40, the actuator 30 cannot rotate unexpectedly due to external impact or vibration applied to the HDD.
FIG. 3A is a cross-sectional view of the HDD of FIG. 1 in a circumferential direction of the disk, for explaining a pitch static angle (PSA) of the slider, and FIG. 3B is a cross-sectional view of the HDD of FIG. 1 in a radial direction of the disk, for explaining a roll static angle (RSA) of the slider.
Referring to FIGS. 3A and 3B, in the HDD, when the head 35 is moved from the ramp 40 and then is loaded onto the disk 20, the slider 34 on which the head 35 is mounted may collide with the surface of the disk 20. In order to avoid the collision, it is necessary to form a stable air bearing between the disk 20 and the slider 34 with the head 35 thereon. However, during the short head loading, very complex hydrodynamic and vibrational phenomena occur between the slider 34 and the disk 20. In particular, static angles, such as the pitch static angle (PSA) θP and the roll static angle (RSA) θR, of the slider 34 formed while the head 35 is moved from the ramp 40 to the disk 20 have a great influence on the collision between the slider 34 and the disk 20. Here, as shown in FIG. 3A, the PSA θP is an inclination of the slider 34 in a rotational direction of the disk 20 with respect to the surface of the disk 20. As shown in FIG. 3B, the RSA θR is an inclination of the slider 34 in a radial direction of the disk 20 with respect to the surface of the disk 20. It is known through many studies that when the PSA θP and RSA θR have positive values, the possibility of collision between the slider 34 and the disk 20 decreases. In further detail, as shown in FIG. 3A, if the PSA θP has a positive value, more air is introduced into a space between the slider 34 and the disk 20, and accordingly, a stronger air bearing is formed in a smoother manner. Thus, the possibility of collision between the slider 34 and the disk 20 is reduced. Similarly, as shown in FIG. 3B, if RSA θR has a positive value when the slider 34 is moved from the ramp 40 to the space above the disk 20, the possibility of collision between the slider 34 and the disk 20 is reduced.
However, even though the PSA θP and RSA θR have positive values, the collision possibility between the slider 34 and the disk 20 may increase depending on the state of the disk 20. That is, the collision possibility varies according to a vertical displacement of a portion of the disk 20 on which the slider 34 is loaded.
FIG. 4 is a graph illustrating a vertical displacement of the disk, for explaining collision between the head and the disk when the head is loaded.
Referring to FIG. 4, when the disk rotates, the disk vibrates. The amplitude of vibration is highest at an edge portion of the disk. The vibration of the disk is caused by deflection of the disk, poor flatness of the disk, and air flow in the HDD. The vibration is periodically repeated whenever the disk rotates. The repeated vibration is called Repeatable Runout (RRO). Because of the RRO, the edge portion of the disk has a vertical displacement repeated over time.
In the related art, the vertical displacement of the disk during head loading has not been considered. Accordingly, as shown in FIG. 4, if the head is loaded on the disk while the vertical displacement of the portion of the disk on which the disk is loaded becomes increasingly greater, a distance between the head and the disk is drastically reduced and thus time is too short to generate sufficient air bearing between the slider on which the head is mounted and the disk. As a result, the collision possibility between the head and the disk increases greatly and also, the impact force applied to the head increases.
As described above, if the head and the disk repeatedly collide with each other, the head and the surface of the disk may be damaged, thereby deteriorating the reliability of the HDD.